STARTING SUNDAY • Bring in a pair of broken or working used headphones and get $10 off any pair of new headphones over $50 at the AC Gears trade-in event. Brands include Audio Technica, Marshall Majors, Zumreed, and AIAIAI. 69 E. 8th St., nr. Mercer St. (212-260-2269); M–S (11–8), Su (noon–7), through 1/31